The 2.7-litre V6 Biturbo. Self-study Programme 198. Service. Design and Function

Transcription

1 198 Service. The 2.7-litre V6 Biturbo Design and Function Self-study Programme 198 All rights reserved. Subject to change. AUDI AG Dept.I/GS-5 D Ingolstadt Fax / Technical status: 01/98 Printed in Germany For internal use only

2 The 2.7-litre V6 biturbo... Turbocharged engines are already something of a tradition at AUDI. The task now facing AUDI s engineers was to develop a worthy successor to the 5-cylinder turbocharged engine. One of the key development goals for the turbocharged engine was to achieve a good level of dynamic response, particularly at the bottom end of the rev band. The goal of AUDI s engineers was to realise a high basic torque level and a torque characteristic that rises in direct proportion to engine speed to its peak. The term basic torque level describes the torque which is immediately available when the throttle is opened (e.g. at part throttle or in overrun). SSP 198/77... a further milestone in engine development by Audi! 2

3 Contents Page Engine... Technical data, crankshaft, cylinder head, camshaft timing, cooling circuit, engine lubrication, overview of components, air ducting, charging, exhaust system, pneumatically controlled systems, charge pressure control, air divert control in overrun, ACF system, crankcase breather Motronic ME Subfunctions, system overview Subsystems of the Motronic... Torque-oriented engine management, torqueoriented functional structure, Electronic throttle, exhaust gas temperature control Sensors... Additional sensors of the Motronic Auxiliary signals/interfaces Functional diagram Self-diagnosis... Vehicle diagnosis, test and information system VAS 5051, test box V.A.G 1598/31 Transmission... Self-adjusting clutch, gearbox This Self-study Programme provides you with information regarding design and function. New! The Self-study Programme is not a Workshop Manual! Important!/Note! Please refer to the Service Literature for all the relevant maintenance and repair instructions. 3

4 Engine The 2.7-litre V6 biturbo This engine will also be used in the Audi S4 and Audi A6. The engine used in the A6 has a comfortoriented setup, which means that it has different torque and power output. This effect was principally achieved by modifying the software configuration of the engine control unit. A tuning protective device prevents the S4 engine control unit being installed in the A6! This prevents misuse, which can result in damage to the drivetrain! An auxiliary heater is not available as an option for the S4 and the A6, due to the constraints on space. BITURBO SSP 198/01 4

5 The technical data 500 S4 200,0 Configuration: V6 engine with 90 V-angle and twin turbochargers ,0 160,0 Engine code: S4: AGB A6: AJK Output: S4: 195 kw at 5800 rpm A6: 169 kw at 5800 rpm Torque [Nm] ,0 120,0 100,0 80,0 60,0 40,0 Output [kw] Torque: S4: 400 Nm at 1850 to 3600 rpm A6: 310 Nm at 1700 to 4600 rpm Maximum speed: 6800 rpm Compression ratio: 9.3 : SSP 198/02 20,0 0, Speed [rpm] Figures obtained using 98 RON unleaded premium fuel to 89/491/EEC. Displacement: 2671 cm 3 A6 Bore: 81 mm ,0 160,0 Stroke: 86.4 mm Weight: approx. 200 kg Engine management: Motronic ME 7.1 Firing order: Fuel type: S4: 98/95/91 RON A6: 95/91 RON Compliant with emission standard: EU III-D Torque [Nm] ,0 120,0 100,0 80,0 60,0 40,0 20,0 0, SSP 198/46 Speed [rpm] Figures obtained using 95 RON unleaded premium fuel to 89/491/EEC. Output [kw] 5

6 Engine The crankshaft The crankshaft is identical to that used in the 2.8-litre V6 engine. The crankshaft bearing caps are attached to the central crankcase by 4 bolts. The 4-bolt connection reduces the load on the bearing caps considerably. The middle two crankshaft bearing caps are also bolted to the side of the crankcase. The lateral bolted connection helps to improve acoustics. The pistons are forged to enable them to withstand the high loads to which they are subjected. Due to the high combustion pressures, a 2- material bearing shell is installed on the connecting rod side. The bearing cap has a 3- material bearing shell. Advantage: The bearing shell has a high load-bearing capacity SSP 198/11 2-material bearing shell 4-bolt connection Lateral bolted connection 3-material bearing shell 6

7 Cylinder head The cylinder heads are largely identical to those used in the V6 naturally aspirated engine. Common parts are used for both banks of cylinders. The mounting position of the right-hand cylinder head is rotated through an angle of 180 in relation to the left-hand cylinder head. The timing of the inlet camshafts is enginedependent. To improve heat dissipation, the exhaust valves are sodium-filled. Tumble duct The shape of the inlet duct causes the drawnin air to tumble. Advantages: A good degree of swirl and high ignitability fuel-air mixture are achieved The tumble effect allows more efficient combustion For a turbocharged engine, the compression ratio of 9.3 : 1 is high. Advantage: High basic torque level and fuel economy In combination with five-valveper-cylinder technology, the inlet duct is shaped as a so-called tumble duct. Tumble effect Tumble duct SSP 198/78 7

8 Engine The variable valve timing The camshaft timing has been modified compared to the 2.8-litre V6 engine to meet the demands of turbocharging technology. Variable valve timing with an adjustment angle of 22 is used here for the first time in turbocharged engines. Advantage: A torque increase of approx. 10% is achieved at the bottom and top ends of the engine speed range. Better emission levels and fuel consumption figures. The design and function of the variable valve timing are already described in Self-study Programmes 182 and 192. Activation of the variable valve timing is dependent on engine load and speed. In the self-diagnosis, you can find out whether the variable valve timing is active or not by reading out the relevant measured value block (refer to Workshop Manual). The variable valve timing is activated by the Motronic by means of camshaft adjustment valves N205 and N208. Diagram of variable valve timing (shown using the 265 bhp engine as an example) Variable valve timing active = advance position Full throttle Engine load in % SSP 198/45 Engine speed 8

9 Cooling circuit Both exhaust gas turbochargers are watercooled and integrated in the cooling circuit. When the coolant thermostat is closed, the coolant flows back to the coolant pump along the short-circuit line as well as the heat exchanger. When the coolant thermostat is open, the coolant flows back to the coolant thermostat through the radiator (primary flow) or through the oil cooler and expansion tank (secondary flow). Located in the cooling circuit is a electrical coolant pump. This pump is required as a means of protection against overheating of the coolant under high thermal load, e.g. when the hot engine is turned off. Coolant temperature senders G2 and G62 Continued coolant function pump Heat exchanger Thermoswitch for F95 Expansion tank Short-circuit line Coolant SSP 198/03 Radiator fan thermoswitch F18/F54 Coolant pump Oil cooler Radiator 9

10 Engine Electrical coolant circulation pump V51 Electrical coolant circulation pump V51 is located in the engine s V angle. If the coolant temperature is too high, thermoswitch for coolant circulation run-on F95 activates the additional coolant function. The high temperatures which occur at the exhaust gas turbocharger produce vapour bubbles which prevent coolant being drawn in by pump V51. When pump V51 starts up, the coolant flows through the exhaust gas turbocharger and the cylinder heads. The direction of flow in the turbocharger cooling circuit is reversed by this. Due to this reversal of the direction of coolant flow, coolant is drawn in via the cylinder heads (large cross-sections), which means that any vapour bubbles which develop are expelled from the exhaust gas turbocharger lines. The electrical coolant circulation pump again draws in coolant along the rear coolant pipe, thereby recirculating the coolant. Thermoswitch for additional coolant function F95 Rear coolant pipe Radiator fan thermoswitch F18/F54 SSP 198/10 Electrical coolant circulation pump V51 10

11 Fan control The control unit for radiator fan V293 regulates the output of the radiator fan and controls the continued coolant circulation. The induced-air fan V7 and the forced-air fan V177 are activated simultaneously. Forced-air fan V177 is located upstream of the condenser, water cooler and visco fan. It assists the visco fan. The electronic power control The various fan settings are executed by an electronic power control. The fan motors are operated periodically, the length of the operating cycle depending on the fan setting selected. Fan output level is controlled via pulse-width-modulated outputs. Should a fan fail, the radiator fan control unit increases the speed of the fan motor still available. Advantages of the power control: The series resistors previously used for power control are no longer required. Lower power consumption in lower fan settings. Safety functions. SSP 198/50 Control unit for radiator fan attached to front right vehicle side member 8-socket relay plate The power supply is protected by a fuse on the 8-socket relay plate. For the correct fuse rating, please refer to wiring diagram. Vehicles equipped with an air conditioner require a higher fuse rating than vehicles without an air conditioner. SSP 198/55 Fuse, terminal 61 Fuse, terminal 30 11

12 Engine Electric circuit of fan control: F18 * V293 M_ Air-conditioning pressure switch F129 * V51 F54 M_ F129 P P V7 M_ V177 * F95 only for vehicles with air conditioner SSP 198/17 for vehicles with air-conditioning system: Integrated in the pressure switch for air conditioner F129 is the high-pressure switch for activating a higher fan setting. The pressure switch is mounted below the right-hand headlight behind the bumper. Components: F18/F54 Radiator fan thermoswitch F95 Thermoswitch for continued coolant function F129 Pressure switch for air conditioner (only for vehicles with air conditioner) V293 Control unit for radiator fan V7 V51 V177 Radiator fan (induced-air fan) Continued coolant circulation pump Fan 2 for radiator (forced-air fan) (only for vehicles with air conditioner) 1 Terminal 30, positive supply via fuse on 8-socket relay plate 2 Terminal 61, D+ (alternator) via fuse on 8-way relay 3 Fan activation (only for vehicles with air conditioner) 12

13 Function of fan circuit (for vehicles with air-conditioning system) 4 fan settings are possible: The electrical coolant function... is activated by coolant pump thermoswitch F95. The fan motors and continued coolant circulation pump V51 are activated. The fan motors run at min. output (40%). The continued coolant function is only activated if the engine not running signal is picked up at terminal 61. The continued coolant function period is limited to 10 minutes. Fan speed 1... is requested by radiator fan thermoswitch F18 or by the air-conditioning control panel. The fan motors run at 50% output. Fan speed 2... is activated by air-conditioning system pressure switch F129. The fan motors run at 85 % output. Fan speed 3... is activated by radiator fan thermoswitch F54. The fan motors run at full output. Fan speeds 1, 2 and 3 are only activated if the engine running signal is picked up at terminal

14 Engine Engine lubrication The oil circuit of the 2.7-litre V6 biturbo engine largely corresponds to that of the 3rd V6 engine generation. In addition, the two exhaust gas turbochargers are supplied with pressurised oil from the main oil gallery via a distributor piece. The oil is returned directly to the oil sump. The oil cooler was adapted to withstand the higher thermal stresses in comparison with a naturally aspirated engine. to oil filter/oil cooler Oil pressure relief valve Restrictor A new feature of the biturbo is the integrated oil supply (see next page). Exhaust gas turbocharger distributor piece Bearing cap Oil groove The oil circuit A duocentric oil pump draws in the oil through a coarse filter. Located in the pressure chamber of the pump is a pressure relief valve which protects downstream components against pressure peaks during cold starts. The oil is fed to the oil filter via the oil cooler. After passing an oil retention valve, the oil flows through the filter element. A bypass filter is connected in parallel with the filter element. Oil retention valve The oil subsequently reaches the main oil gallery. A branch line is routed to the oil pressure control valve (clean oil side). Oil retention valves Filter element The following components are supplied with oil from the main oil gallery: - the four crankshaft bearings - the two exhaust gas turbochargers via an oil distributor line - the three pairs of piston spray jets via a spray jet valve - the cylinder head of cylinder bank 1 via an oil retention valve from oil filter/oil cooler Main oil gallery The cylinder head of cylinder bank 2 is supplied through a separate bore from crankshaft bearing 2 via an oil retention valve also. Spring-loaded slipper (chain tensioner) Oil pressure control valve Induction filter Oil temperature sender SSP 198/49 Oil pressure switch Bypass filter First of all, the camshaft adjustment valve is supplied with oil from the inlet drilling in the cylinder head. After the oil has passed by a restrictor, it is channeled via the cylinder head main gallery to the hydraulic valve tappets and the camshaft bearings. Oil pressure relief valve from oil filter/oil cooler to oil filter/oil cooler Bypass valve 14 15

15 Engine The component parts of the oil circuit The oil pump... is an internal gear pump. It is attached to the crankcase as a separate component. The oil pump is designed in such a way that it projects deep down into the oil sump and is immersed completely in the engine oil when the oil level is correct. This prevents the oil pump running dry. The oil pump, in combination with the extremely short intake path, enables oil pressure to build up more quickly and safely, particularly during cold starts. The oil pump is driven by the crankshaft by means of a single chain. A spring-loaded flat plate produces the necessary tension. A new feature of the oil pump is the chain guard made from sheet steel. It encapsulates both the chain wheel and the chain over a large area. This reliably prevents oil frothing and the problems associated with this. Oil pressure limiting valve SSP 198/57 The oil filter... Oil pressure control valve Chain guard contains an oil retention valve, the filter element, a bypass filter and the filter bypass valve. The latter has the task of maintaining engine lubrication via the bypass filter if the filter element becomes clogged up or if the oil has a high viscosity. The oil cooler... is integrated in the primary flow. By increasing the capacity and optimising the flow resistance, the entire oil flow can be routed through the oil cooler. Unlike the V6 naturally aspirated engine, a bypass is not required. The spray jets valve... opens up the oil flow to the piston spray jets if the oil pressure is greater than 1.8 bar. Reason: at low oil viscosity and low engine speeds, the oil pressure would otherwise drop below the minimum permissible level. That aside, piston cooling is not necessary at low engine speeds. 16

16 The oil pressure control valve... regulates the engine oil pressure. It is integrated in the oil pump housing. The oil quantity regulated by the oil pressure control valve is fed to the suction side of the oil pump. This helps to optimise efficiency. The oil retention valves... prevent the oil running out of the oil filter and the cylinder heads and back into the oil sump while the engine is stationary. The oil pressure limiting valve... is a pressure relief valve. It is located inside the oil pump housing and opens when the oil pressure rises too high (cold start). If an excessively high oil pressure builds up, various component parts of the oil circuit (e.g. oil filter, oil cooler) may be damaged. Also, there is the possibility of the inlet and exhaust valves opening or no longer closing, due to bulking of the hydraulic tappets. The knockon effect of this is that the engine can no longer be started or cuts out. The restrictors... prevent flooding of the cylinder heads. At high engine speeds, an excessively large amount of oil enters the cylinder heads and has to be returned to the oil sump via the oil return drillings. The restrictors reduce the oil flow and thereby ensure that return flow takes place. The integrated oil supply... Transverse drilling will also be adopted for all V6 5V naturally aspirated engines. Each camshaft bearing is supplied via a drilling stemming from the cylinder head main gallery. The oil is fed along a bolt shaft in the bearing cap to a transverse drilling. A lubrication groove distributes the oil throughout the camshaft bearing. It is no longer necessary to run a pipe to the individual bearing caps. Advantages: Fewer components Quick and even oil supply No additional installation work necessary Lower cost SSP 198/58 Cylinder head main gallery 17

17 Engine Front view of engine Hall sender G163 Intake-air temperature sender G42 Knock sensor G61 Knock sensor G66 Charge air cooler Camshaft adjustment valve N208 Charge air cooler SSP 198/51 Power assisted steering pump drive Oil pressure switch Alternator Visco fan Oil filter Air-cond. compressor 18

18 Rear view of engine Hall sender G40 Pressure limiting valve Distributor piece Coolant temperature sender F18/F54 Camshaft adjustment valve N205 Thermoswitch for continued cooling function F95 Exhaust gas temperature sender G235 (with evaluation electronics) SSP 198/52 Lambda probe G108 Prim. catal. converter Exhaust gas temperature sender G236 (with evaluation electronics) Lambda probe G39 Prim. catal. converter SAC clutch pressure plate 19

19 Engine Top view of engine Camshaft adjustment valve N205 Solenoid valve for charge pressure control N75 Solenoid valve for activated charcoal Divert air valve for turbocharger N249 Fuel pressure regulator Injector Injector Divert air valve Hall sender G163 Charge pressure sender G31 Throttle valve control part Divert air valve SSP 198/54 Camshaft adjustment valve N208 20

20 View of engine from left Injector Pressure control valve Individual ignition coil Prim. catal. converter SSP 198/53 Charge air cooler Oil filter Oil cooler Pressure unit for wastegate flap Exh. gas turbocharger 21

21 Engine Air ducting Fresh air is induced by the combined air filter and air mass meter and distributed to the two exhaust gas turbochargers by the air distributor. The air distributor is made of plastic. Advantage: Lower weight The intake air is heated to a lesser degree by the engine The air, which is compressed and thus heated by the exhaust gas turbocharger, is fed to the charge air coolers. Cooling air intakes in the bumper and air vents in the wheel housing liners ensure that a sufficient amount of air flows through the charge air coolers. Advantage of charge air cooling: Cooled air has a higher density, and this means improved volumetric efficiency. The lower temperature reduces knock tendency also. The compressed air streams then converge upstream of the throttle valve control part and distributed to the individual cylinders in the intake manifold. Exhaust gas turbocharger Air filter Air mass meter Air distributor Throttle valve control part SSP 198/04 Charge air cooler 22

22 Charging Two water-cooled exhaust gas turbochargers with wastegate are used for charging. The charge pressure of both exhaust gas turbochargers is controlled via the common charge pressure control valve N75. Advantages of the biturbo technology: The exhaust gas turbocharger is smaller, which means better response due its reduced mass. Higher charge pressure at low engine speeds. The exhaust gas turbochargers are located outside the V-angle due to the high temperatures they reach. This advantage of this arrangement is that the intake air is not heated up additionally and the subassemblies are not subjected to so much thermal stress. Since the turbochargers are flanged directly onto the exhaust manifold, the exhaust gases travel less distance and there is less temperature loss. As a result, the catalytic converters are able to heat up more quickly and the efficiency of the exhaust gas turbocharger is improved by the favourable air-flow. The turbochargers must be replaced in pairs To maintain a synchronous air-flow through the two chargers, it is important to observe this instruction to account for manufacturing tolerances. Service personnel are not permitted to adjust the linkage to the wastegate flap. Compressor housing Exhaust manifold Pressure unit for actuating wastegate flap to exhaust system SSP 198/32 Turbine housing Charge press. side of exh. gas turbocharger Control pressure from solenoid valve for charge pressure control Intake side of exhaust gas turbocharger 23

23 Engine Exhaust system The exhaust manifolds are designed as pipe elbows with insulated air gaps. Advantage: Less heat loss of the exhaust gas and less heat radiation in the engine compartment Weight saving Located downstream of each exhaust gas turbocharger is a primary catalytic converter close to the engine (metal substrate). Advantage The catalytic converters quickly reach a state of readiness for operation after a cold start A new generation of probes is used in this engine. The planar lambda probe is an improvement on the finger-type lambda probe (refer to chapter on Sensors ). Advantage: Short warm-up time Less heating energy demand Long service life More stable control characteristic The large-surface area main catalytic converters (ceramic substrate) are located under the vehicle floor. Exhaust manifold Air-gap-insulated pipe elbow Inner pipes Outer shell Wire mesh ring acting as a spacer Lambda probe SSP 198/33 Main catalytic converter Prim. catal. converter 24

24 Pneumatically controlled systems In the Biturbo, 4 systems are pneumatically controlled: Charge pressure control The Motronic ME 7.1 activates the solenoid valve for charge pressure control N75 and regulates the charge pressure via the wastegate. Divert air control in overrun The Motronic ME 7.1 activates the electric divert air valve for the turbocharger and opens the pneumatic divert air valves using this vacuum. ACF system The Motronic ME 7.1 activates the solenoid valve for the activated charcoal canister and regulates the fuel vapour feed rate to the engine via the vacuum. Crankcase breather The crankcase breather controls the return of oil vapours to the engine via two mechanical valves. For exact the line routing, please refer to the Workshop Manual. Non-return valve (divert air control in overrun) Divert air valve for turbocharger N249 Divert air valve (pneumatic) Non- return valves (ACF system) Solenoid valve for activated charcoal canister N80 SSP 198/31 Pressure control valve Distributor piece Solenoid valve for charge pressure control N75 25

25 Engine Charge pressure control The air mass required to develop a specific level of torque is determined by means of an air mass calculation and produced by controlling the charge pressure as required. For safety reasons, the engine in the biturbo regulates the charge pressure, and not the air mass as is the case with the 1.8-litre 4-cylinder turbocharged engine. The charge pressure is measured by charge pressure sender G31. The Motronic regulates the charge pressure of both turbochargers via the solenoid valve for charge pressure control G31. If a defect occurs in one of the cylinder banks (e.g. melting of the catalytic converter or blockage of the exhaust system), a purely air mass-oriented charging system would still try to provide the computed air mass. This would lead to an excessively high charge pressure. In any case, the charge pressure control prevents an excessively high charge pressure building up inside the intake system. Charge pressure Atmospheric pressure Control pressure SSP 198/08 Solenoid valve for charge pressure control N75 Charge pressure sender G31 26

26 The solenoid valve for charge pressure control N75 changes the opening time to atmospheric pressure according to the signals it receives from the engine control unit (duty cycle). Thus, a control pressure is produced by modulating the charge pressure and atmospheric pressure. This pressure acts on the pressure unit for the wastegate. The wastegate is kept closed in a depressurised state by a spring inside the pressure unit. The entire exhaust gas flow is routed via the turbine, and a charge pressure is built up. The control pressure counteracts this spring force and opens the wastegate. Part of the exhaust gas flow is fed from the wastegate past the turbine, and the charge pressure stops rising. Turbine wheel Impeller to catalytic converter Intake air Wastegate flap (open) Control pressure from solenoid valve for charge pressure control pressure unit N75 Exhaust gas from combustion chamber SSP 198/66 charge pressure to solenoid valve for charge pressure control N75 to combustion chamber If there is no flow, N75 is closed and the charge pressure acts directly on the pressure unit. The waste gate opens even if the charge pressure is low. If the charge pressure control fails, the charge pressure is thus limited to a basic charge pressure in order to prevent the maximum permissible charge pressure being exceeded. This results in a loss of performance. The basic charge pressure is the charge pressure (approx mbar) which is achieved without regulation (mechanical charge pressure). Atmospheric pressure from distributor piece Restrictor SSP 198/67 Solenoid valve for charge pressure limitation N75 Control pressure to pressure unit Passage in no flow state Charge pressure from compressor housing 27

27 Engine Divert air control in overrun To avoid pumping the exhaust gas turbochargers when a sudden transition from high load to overrun is made, two divert air valves are used. The Motronic also activates the two pneumatic divert air valves by means of an electrical changeover valve, the divert air valve for turbocharger N249. Advantage: Controlled opening of the divert air valves reduces the noise level in the induction tract and reduces fuel consumption. The divert air valve N249, in combination with the vacuum reservoir, enables the divert air valves to operate independently of the intake manifold pressure. The system is designed in such a way that the pneumatic divert air valves continue to be opened by the intake manifold pressure if the electrically actuated divert air valve N249 fails. Vacuum reservoir (inside wheelhousing on the left) with flow without flow Divert air valve for turbocharger N249 Non-return valve SSP 198/05 Divert air valve (pneumatic) 28

28 ACF system Integrated in the lines of the ACF systems are the solenoid valve for activated charcoal canister N80 and two non-return valves. The engine control unit, assisted by solenoid valve N80, regulates the return rate of the fuel vapours from the ACF canister. The Motronic operates the solenoid valve cyclically using a pulse duty cycle. The non-return valves control the return of fuel vapours, depending on operating state. Vacuum in intake manifold: Non-return valve 1 open. Fuel vapours return to intake manifold. charge pressure in intake manifold: Non-return valve 2 open. Fuel vapours return upstream of exhaust gas turbocharger. For the exact line routing, please refer to the Workshop Manual. ACF canister Solenoid valve for activated charcoal canister N80 Non-return valve 1 Non-return valve 2 SSP 198/06 Vacuum in intake manifold Charge pressure in intake manifold 29

29 Engine The crankcase breather......comprises a distributor piece, a pressure limiting valve, a non-return valve and the associated hoses. The oil vapours and blow-by gases from the cylinder heads and the crankcase converge in the distributor piece. The pressure limiting valve and the non-return valve control the return of these vapours and gases to the engine, depending on the intake manifold pressure. Vacuum in intake manifold: The oil vapours and blow-by gases return via the non-return valve in the intake manifold. charge pressure in intake manifold: The oil vapours and blow-by gases return via the pressure limiting valve in the air distributor. The pressure limiting valve limits the vacuum in the crankcase. If the vacuum in the crankcase exceeds a defined value, the diaphragm is drawn over the connection against the force of the spring and closes the connection. The valve is designed in such a way that it allows a small quantity to pass through when closed. This prevents the engine oil being drawn into the intake tract and has no adverse effects on engine breathing. The term blow-by gases refers to the gases which escape from the combustion chamber past the piston rings. Distributor piece Pressure limiting valve from distributor piece Air distributor to air distributor Connection Diaphragm SSP 198/07 Non-return valve 30

30 Motronic ME 7.1 Subfunctions of the Motronic The Motronic consists of known and new subfunctions: Sequential injection Charge pressure control (see chapter on Engine pp. 26 and 27) λ Stereo lambda control Mapped ignition Cylinder-selective knock control Static high-tension distribution with 6 individual ignition coils ACF system Torque-oriented engine management New Electrically actuated throttle valve (Electronic accelerator) New Cylinder bank-specific exhaust gas temperature control New Mapped variable valve timing (intake camshaft adjustment) (see chapter on Engine p. 8) New SSP 198/44 31

31 Motronic ME 7.1 Sensors Actuators Hot-film air mass meter G70 Fuel pump relay J17 and fuel pump G6 Engine speed sender G28 Injectors (bank 1) N30, N31, N32 Control unit for Motronic J220 Hall senders (bank 2) G40 and (bank 1) G163 Injectors (bank 2) N33, N83, N84 Lambda probes (bank 1) G39 and (bank 2) G108 SSP 198/14 Output stage (bank 1) N122 and ignition coils N (cyl. 1), N128 (cyl. 2) and N158 (cyl. 3) Throttle valve control part J338 with angle sender (1) G187 and (2) G188 for throttle valve drive G186 Output stage 2 (bank 2) N192 and ignition coils N163 (cyl. 4), N164 (cyl. 5) and N189 (cyl. 6) Intake air temperature sender G42 Coolant temperature senders G2 and G62 Solenoid valve for activated charcoal canister N80 Charge pressure sender G31 Diagnosis Solenoid valve for charge pressure control N75 Knock sensors (bank 1) G61 and (bank 2) G66 Throttle valve control part J338 with throttle valve drive G186 Accelerator position sender G79 and 2 G185 Camshaft adjustment valve (bank 1) N205 and (bank 2) N208 Exhaust gas temperature senders (bank 1) G235 and (bank 2) G236 Divert air valve for turbochargers Brake light switch F and brake pedal switch F 47 Clutch pedal switch F36 Auxiliary signals Altitude sender F96 is integrated in the engine control unit. EPC Heater for lambda probe (bank 1) Z19 and (bank 2) Z28 Fault lamp for electric throttle control K132 Auxiliary signals 32

32 Subsystems of the Motronic Torque-oriented engine management The Motronic ME 7.1 has a torqueoriented functional structure. This is made possible by the new electronic accelerator function. Making allowance for efficiency and the emissions standards, the engine control unit coordinates the external and internal requests and meets them by adjusting the available control variables accordingly. Internal torque requests External torque requests Driver inputs Starting Idling speed control Catalytic converter heating Power limiter Driving comfort Components protection Engine governing Control variables influencing torque Driving dynamics Driving comfort Coordination of torque and efficiency requests in engine control unit Throttle valve angle Charge pressure Ignition angle Cruise control system Injection cut-out Injection time SSP/198/15 33

33 Subsystems of the Motronic Torque-oriented functional structure In comparison with previously known systems, the ME 7.1 is not confined to the output of torque variables to the networked control units (ABS, automatic gearbox), it also uses these physical variables to calculate control variables. All - internal and external - torque demands are combined, and a nominal torque is derived from this. To translate the nominal torque into actions, the control variables are co-ordinated with regard to consumption and emissions so as to optimise torque control. Nominal charging moment Nominal charge Prioritisation of charging path Conversion of torque into charge Calculation of throttle valve opening Throttle valve angle External and internal torque requests Actual charge Calculation of efficiency and torque reference variables Charge pressurecontrol Nominal intake manifold pressure Charge pressure (Wastegate) Prioritisation of crankshaftsynchronous path Calculation of crankshaftsynchronous intervention Ignition angle Injection cutout Injection time SSP 198/75 Nominal inner torque 34

34 The control variable calculation is subdivided into two paths Prioritisation of charging path Prioritisation of crankshaftsynchronous path Path 1 The charging path regulates the control variables which influence charging: Throttle valve angle Charge pressure Path 2 All control actions which influence torque regardless of charging are combined in the crankshaft-synchronous path: Ignition angle Injection cut-out Injection time The air mass necessary to develop a specific torque is determined by means of a calculation model and is made available along path 1. Path 2 is used to set the injection quantity or cylinder cut-out necessary under the given circumstances and the optimal ignition angle. By and large, long-term torque requests are fulfilled along path 1. Path 2 is particularly well suited to meeting short-term torque requests, which usually have a torque-reducing effect. 35

35 Subsystems of the Motronic Electrically actuated throttle valve (electronic accelerator) With the Motronic ME 7.1, Audi is using an electrically actuated throttle valve for the first time. There is no longer any need for a mechanical accelerator cable between the accelerator and throttle valve. This has been replaced by an electronic control system (drive-by-wire). The system comprises the following components: Accelerator position sender Engine control unit throttle valve control part The accelerator position sender records the accelerator pedal angle and transfers it to the engine control unit. The engine control unit adjusts the throttle valve by means of an electric motor. A continuous stream of feedback signals on the position of the throttle valve is sent to the engine control unit. Extensive security measures in hardware and software format - such as twin senders, safety module and self-monitoring computer architecture - are integrated in the electronic accelerator. CPU = Control Processing Unit Throttle valve control part J338 Input signals Engine control unit Output signals Throttle valve drive G186 Accelerator position sender CPU SSP 198/09 Accelerator position senders G79 and G185 Safety module Angle sender for throttle valve drive G187 and G188 36

36 The electronic accelerator controls the engine output electronically and, over and above intake-air control, offers the advantage that functions such as idling speed control, cruise control or engine governing can be executed easily and comfortably.. The electronic accelerator is used for reducing and increasing torque and does not adversely affect exhaust emissions. Torque reduction Torque increase Traction control system Engine governer Speed limiter Power limiter Cruise control system Driving dynamics control systems Cruise control Engine braking torque control Load change damping (Dash pot function) Idling speed control Driving dynamics control systems The throttle valve can be opened regardless of the accelerator position, and this serves to reduce throttle losses. The ideal combination of throttle valve crosssection and charge pressure produce the necessary torque. In this way, the throttle valve can be opened fully while the accelerator pedal has not been fully depressed. With electronic accelerator, much improved emissions and higher fuel economy are achieved in specific load states. Over and above this, any accelerator characteristic can be programmed, e.g. gradual acceleration when driving at low speed. 37

37 Subsystems of the Motronic Accelerator position senders G79 and G185 The accelerator position sender transfers an analog signal corresponding to the accelerator position to the Motronic. To ensure that the electronic accelerator functions reliably, the accelerator position sender has two independent potentiometers (G79 and G185). They have different characteristic curves (see diagram). The control unit monitors the two senders G79 and G185 for proper functioning and plausibility. If a sender fails, the other sender serves as a substitute. The accelerator position sender transfers the driver s inputs to the Motronic and provides kickdown information to the automatic gearbox. There is no separate switch for kickdown information. Integrated in the accelerator position sender is a mechanical pressure point which conveys an authentic kickdown feel to the driver. When the driver operates the kickdown, the full-load voltage of the accelerator position sender is exceeded. If a voltage defined in the engine control unit is attained in the process, this is interpreted as a kickdown and transferred to the automatic gearbox (via CAN-Bus). The accelerator position senders for the manual gearboxes and automatic gearboxes are identical. Kickdown is enabled or disabled via the accelerator limit stop (refer to chapter on TDI engines ). SSP 198/25 Lever Resistance in Ω LL G79 G185 Accelerator travel SSP 198/12 Acc. position sender Accelerator 38

38 Self-diagnosis/emergency running If a fault occurs in the accelerator position sender or the wiring, two emergency running programs can be run depending on fault type. Emergency running program 1 If an accelerator position sender fails: Accelerator position limited to a defined value. If a full load is predefined, the power output is increased slowly. In the case of implausible signals between G79 and G185, the lower value is used. Prerequisite: The idling speed position must be learnt once by the intact sender. The signal supplied by brake light switch for brake pedal switch F47 indicates the idling speed. Comfort functions (CCS) are prohibited. The fault lamp for electric throttle control K132 comes on. At idling speed, the accelerator position senders G79 and G185 are not diagnosed. If the plug of the accelerator position sender drops off, no fault is stored in the control unit. The fault lamp for electric throttle control K132 does not come on. The engine runs at idling speed and does not respond to the accelerator pedal. Emergency running program 2 If both accelerator position senders fail, driver input recognition is not possible: The engine only runs at idling speed. The fault lamp for electric throttle control K132 comes on. Safety function: For safety reasons, the throttle valve is closed as far as a defined angular position when both the accelerator pedal and the brake pedal are depressed. If the brake is pressed first followed by the accelerator pedal, the driver input (torque request) is executed. 39

39 Subsystems of the Motronic throttle valve control part J338 with throttle valve drive G186, angle senders 1 G187 and 2 G188 for throttle valve drive The throttle valve control part comprises throttle valve housing with throttle valve... throttle valve drive G186 with reduction gear... angle senders for throttle valve drive G187 and G188 Activated by the engine control unit, the throttle valve drive controls the air-flow rate necessary to develop the required torque. Feedback on momentary throttle valve position is provided by two potentiometers G187 and G188. For safety reasons, two angle senders (redundancy) are used. They have opposite impedance characteristics (see diagram). If an angle sender fails, the second sender maintains the electronic accelerator function via an emergency running program. Angle senders G187 and G188 cannot be replaced separately. The throttle valve control part may not be opened. Redundancy means: superfluous, non-essential. Throttle valve housing with throttle valve Throttle valve drive G186 (Electric throttle control) Resistance in Ω 0 100% Throttle valve opening in % SSP 198/27 G188 G187 SSP 198/28 Angle senders for throttle valve drive G187 and G188 Housing cover with electrical connections 40

40 Functional positions of throttle valve control part (linear representation) The engine control unit recognises four key functional positions of the throttle valve control part. The lower mechanical limit stop The throttle valve is closed. This position is required to adapt the angle sender. Lower mechanical limit stop SSP 198/24 The lower electrical limit stop is defined by the control unit and is located just below the lower mechanical limit stop. During operation, the throttle valve closes no further than the lower electrical limit stop. This prevents the throttle valve working its way into the throttle valve housing. Position of lower electrical limit stop SSP 198/22 The emergency running position is the position of the throttle valve in the deenergised state and ensures that air flow is sufficient if any of the relevant electronic accelerator functions fails. Idling speed is higher - approx rpm - and uneven. Very limited vehicle operation is possible. Emergency running position SSP 198/21 41

41 Subsystems of the Motronic The upper electrical limit stop is defined in the control unit does not need to be learned. Position at upper electrical limit stop As in the fully open position, the shaft diameter is greater than the thickness of the throttle butterfly. SSP 198/23 Upper mechanical limit stop To enable the exact angular position of the throttle valve to be identified, angle senders for throttle valve drive G187 and G188 must be learnt. By moving the throttle valve into predefined positions, the values of the angle senders are stored in the control unit (calibrated) and checked for plausibility. The state of the mechanics (terminals, weak springs) in the throttle valve control part is determined by evaluating the throttle valve s reaction speed. Basic adjustment (adaption) involves not only learning the throttle valve position, but also a complete check of the throttle valve control part... can be performed using the following three methods: manually - provided the ignition has been switched on for at least 24 minutes without operating the starter or accelerator. automatically - provided the need for adaption is acknowledged. specifically - by initiating basic setting 04 in measured value block 60 (refer to Workshop Manual) Adaption conditions For basic setting (adaption), the test conditions described in the Workshop Manual must be met. The basic setting routine will be cancelled if the test conditions are not fulfilled while it is in progress. 42

42 Self-diagnosis/emergency running mode If a fault occurs in the throttle valve control part or in the wiring, three emergency running programs can be run, depending on fault type. Emergency running program 1 If an angle sender for throttle valve drive fails or an implausible signal is received: Torque-increasing requests on engine, e.g. CCS, EBC (engine braking control) are suppressed. The fault lamp for electrical throttle control K132 comes on. Prerequisite: An intact angle sender and plausible air mass flow. The air mass flow is indicated by the air mass meter and the charge pressure sender G31. Emergency running program 2 If the throttle valve drive fails or malfunctions: The throttle valve drive is switched off and the throttle valve goes into the emergency running position. This results in considerable loss of power, increased idling speed and possibly also rough idling. Driver inputs are executed as far as possible via the ignition angle and charge pressure. The engine shows little response to the throttle. The fault lamp for electrical throttle control K132 comes on. Prerequisite: Emergency running program 2 is only run if both angle senders for throttle valve drive recognise the emergency running position. Emergency running program 3 If the throttle valve position is not clearly recognisable and/or if the throttle valve is not definitely known to be in the emergency running position: The throttle valve drive is switched off and the throttle valve goes into the emergency running position. This results in considerable loss of power, increased idling speed and possibly also rough idling. The engine speed is limited to approx rpm by restricting the injection. The fault lamp for electric throttle control K132 comes on. Repair work may not be performed on the throttle valve control part J338! If G186, G187 or G188 becomes faulty, unit J338 must be replaced completely and a basic setting performed. 43

43 Subsystems of the Motronic Fault lamp for electric throttle control K132 Faults in the Electronic Accelerator System are detected by the self-diagnosis and indicated via the separate EPC fault lamp. At the same time, an entry is made in the fault memory. EPC stands for Electronic Power Control. When the ignition is turned on, the fault lamp comes on and must go out again after 3 seconds if a fault state does not exist. Fault lamp K132 is activated directly by the engine control unit via an earth potential. If a fault occurs in the Electronic Accelerator System, an appropriate emergency running program will be activated (refer to Accelerator position sender and throttle valve control part). EPC C EPC C 8 1/2 1/ Volt SSP 198/47 44

44 In keeping with our policy of continuous product improvement, the accelerator position sender has been replaced by the accelerator pedal module. The accelerator pedal module has already been used in other vehicle models within the Group. The accelerator pedal module combines the accelerator pedal and the accelerator position sender as a unit. The mechanics of the accelerator pedal module are located inside the module housing. Sensors G79 and G185 are located in the housing cover. Advantages of the accelerator pedal module: Compact, lightweight, easy to assemble Modular technology Inexpensive to manufacture For manual gearbox: Stop buffer For automatic gearbox: Pressure element for conveying the authentic feeling of a kickdown Module housing Housing cover and sensors SSP 198/34 45

45 Subsystems of the Motronic Exhaust gas temperature control A new feature of Audi automobiles is a function which monitors exhaust gas temperature over the entire engine speed range. For turbocharged engines, the maximum permissible exhaust gas temperature is a key design criterion. To protect the exhaust gas turbocharger and the exhaust manifold, the exhaust gas temperature should not exceed 1000 C for a lengthy period of time. Since many of the components which influence the exhaust gas temperature have tolerances, thermodynamic adaptation previously took place at 950 C for safety s sake. This was achieved by enriching the air/fuel mixture. The exhaust gas temperature is recorded in a cylinder-bank-specific manner by the two exhaust gas temperature senders G235 and G236. The Motronic controls the exhaust gas temperature to 980 C by enriching the air/fuel mixture. It is therefore possible to largely dispense with the prophylactic enrichment process that has been standard practice until now. The mixture is only enriched when necessary and... to the extent necessary. This means that engine operation with lambda = 1 is possible up to high load and engine speed ranges. Advantage: Improved efficiency and reduction of fuel consumption as well as exhaust emissions. Exhaust gas temperature sender G235 Engine control unit Injectors G236 SSP 198/26 46

46 Exhaust gas temperature sender G235 and G236 evaluation electronics To facilitate exhaust gas temperature control, the exhaust gas temperature must be recorded to a high degree of accuracy. An accuracy of ± 5 C is achieved in the measurement range from 950 C to 1025 C. The exhaust gas temperature sender is located inside the exhaust manifold upstream of the exhaust gas turbocharger. It comprises a measuring sensor and evaluation electronics. The measuring sensor and the control unit are permanently connected by means of a shielded, heat-resistant wire. Meas. The evaluation electronics convert the signal which the measuring sensor generates into a pulse-width-modulated signal (PWM signal). This is a square-wave signal with a fixed frequency and a variable pulse duty factor. The pulse duty factor is expressed as a percentage. The measurement range extends from 10% to 90%. A specific pulse duty factor is assigned to each temperature (refer to diagram). Substitute function and self-diagnosis: A pulse duty factor of <1% or >99% is recognised as a fault. A fault is detected as of a certain enrichment quantity. If a sender fails, the charge pressure is reduced to a safe level and an emergency enrichment characteristic (engine speed-dependent) is used. 90% SSP/198/13 Exhaust gas temperature sender Pulse duty factor 70% 50% 30% 10% 945 C 950 C 960 C SSP 198/ C 980 C 990 C 1000 C 1010 C 1025 C 1030 C Exhaust gas temperature 47

47 Notes 48

48 Sensors The following chapter presents the new features of the sensors, provided that they have not already been described in the chapter on Subsystems of Motronic. Charge pressure sender G31 The charge pressure sender is located upstream of the throttle valve control part. The Motronic supplies the sender with a voltage of 5 volts and earth. The signal which the sender generates is a pressure- proportional voltage ranging from 0 to 5 volts. SSP 198/29 At atmospheric pressure (at sea-level), the voltage is approx. 2.5 volts. The signal is used for charge pressure control. The Motronic also needs information on charge pressure so that it can take countermeasures if the maximum permissible pressure is exceeded. Substitute function and self-diagnosis: If sender G31 fails, the charge pressure is controlled via the characteristic curve (engine speed-dependent). This will result in a deficiency of engine power. Charge pressure sender G31 The altitude sender F is integrated in the engine control unit, as is normally the case with turbocharged engines.... is required to control the charge pressure. In conditions of decreasing air pressure (lower density), the charge pressure is reduced to prevent the turbocharger overspeeding.... influences the air/fuel mixture composition at engine start-up. The starting mixture is leaned down with rising altitude. Substitute function and self-diagnosis If a signal fails, the charge pressure is reduced to a safe level, which results in a deficiency of engine power. Adaption of the injection quantity at start-up no longer takes place. The fault message Control unit defective is displayed in the self-diagnosis. 49